Personally I use a very very mild washing liquid detergent (as in a couple of drops per litre or so) to gently wipe over all the plastic surfaces in the car. I find the detergent helps to remove greasy marks/build up.
As for seats I use some leather cleaner and conditioner that came with the sofa...
When this runs out though, I'll switch to another brand and continue with the conditioning.
I also find the glass rarely requires window cleaning solutions... damp cloth followed by drying with another dry cloth seems to do the trick.